Our purpose is to determine the source of lipoprotein (a) (Lp(a)) in humans using amino acids labeled with stable isotopes. Apoprotein B (apoB) and apo (a) kinetics will be examined using [2H4]-lysine. [15N]- glycine, and [13-C] leucine incorporation into the apoproteins. Precursor-Product relationships will be examined using curve peeling techniques to determine if Lp(a) is directly secreted or a product of lipoprotein metabolism.